TDD (Time Division Duplex)

Time Division Duplex uses one frequency band for both uplink and downlink, alternating between them in time. TDD is the dominant duplexing scheme for 5G mid-band (3.5 GHz), most Wi-Fi, and many enterprise small-cell deployments, because it can flexibly allocate capacity between directions and avoids the need for paired spectrum.

Categories: Radio Access NetworkSignalingSecurity Controls

TDD in context

The radio access network is where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations and downgrade attacks; defenses rest on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

Signaling protocols carry the control-plane messages that set up calls, register subscribers and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA as top-tier telecom risk.

To place TDD in the wider telecom-security picture, review 1G, ITU, Lawful Interception, RADIUS, RTP and SIP — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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